Measuring the risk of an Australian Zika outbreak

The conditions have been right for Zika virus to spread during the warmer months of past years in Townsville, Cairns and Rockhampton, according to research led by the Australian Red Cross Blood Service.

Using temperature data from January 2015 to December 2016, the team modelled the ability of mosquitoes to spread the virus in four Queensland cities. Brisbane (the fourth city) was the only site where the risk was low.

“If locations experience outbreaks of dengue, the conditions would also be right for outbreaks of Zika,” says lead researcher Dr Elvina Viennet.

The findings emphasise the need for imported cases to be reported immediately, Elvina says.

“We need increased investment in monitoring mosquito populations, and preventative strategies to address the ongoing risks presented by Zika and similar viruses.”

Infected Aedes aegypti and Aedes albopictus mosquitoes are the main transmitters of the disease (along with dengue and chikungunya viruses). Between 50 to 80 per cent of infected people don’t show symptoms, posing challenges for detection and risk management.

Their analysis included estimating average daily biting rate of the mosquitoes, temperature, probability per bite of virus transmission, mosquito death rate, and the incubation period (time from infection to showing symptoms).

“We’re now using a more complex equation involving future climate change scenarios—because if the temperature is warming, the model and how quickly the virus is transmitted may also change,” says Elvina.

In Australia, the risk of transmission via blood transfusion is extremely low. The Blood Service has very strict prevention measures in place, including a questionnaire asking where people have recently traveled.

Australian governments fund the Blood Service to provide blood, blood products and services to the Australian community.